In the late 1800's, Thomas Edison invented the light bulb. The conventional light bulb, commonly called the “Edison bulb,” has been used for over one hundred years for a variety of applications including lighting and displays. The conventional light bulb uses a tungsten filament enclosed in a glass bulb sealed in a base, which is screwed into a socket. The socket is coupled to an AC power or DC power source. The conventional light bulb can be found commonly in houses, buildings, and outdoor lightings, and other areas requiring light or displays. Unfortunately, drawbacks exist with the conventional light bulb:                The conventional light bulb dissipates more than 90% of the energy used as thermal energy.        The conventional light bulb routinely fails due to thermal expansion and contraction of the filament element.        The conventional light bulb emits light over a broad spectrum, much of which is not perceived by the human eye.        The conventional light bulb emits in all directions, which is undesirable for applications requiring strong directionality or focus, e.g. projection displays, optical data storage, etc.        
To overcome some of the drawbacks of the conventional light bulb, several alternatives have been developed including fluorescent lamps, Mercury vapor lamps, sodium vapor lamps, other high-intensity discharge (HID) lamps, gas discharge lamps such as neon lamps, among others. These lamp technologies in general suffer from similar problems to Edison lamps as well as having their own unique drawbacks. For example, fluorescent lamps require high voltages to start, which can be in the range of a thousand volts for large lamps, and also emit highly non-ideal spectra that are dominated by spectral lines.
In the past decade, solid state lighting has risen in importance due to several key advantages it has over conventional lighting technology. Solid state lighting is lighting derived from semiconductor devices such as diodes which are designed and optimized to emit photons. Due to the high efficiency, long lifetimes, low cost, and non-toxicity offered by solid state lighting technology, light emitting diodes (LED) have rapidly emerged as the illumination technology of choice. An LED is a two-lead light source typically based on a p-i-n junction diode, which emits electromagnetic radiation when activated. The emission from an LED is spontaneous and is typically in a Lambertian pattern. When a suitable voltage is applied to the leads, electrons and holes recombine within the device releasing energy in the form of photons. This effect is called electroluminescence, and the color of the light is determined by the energy band gap of the semiconductor.
Appearing as practical electronic components in 1962 the earliest LEDs emitted low-intensity infrared light. Infrared LEDs are still frequently used as transmitting elements in remote-control circuits, such as those in remote controls for a wide variety of consumer electronics. The first visible-light LEDs were also of low intensity, and limited to red. Modern LEDs are available across the ultraviolet and infrared wavelengths, with very high brightness.
The earliest blue and violet gallium nitride (GaN)-based LEDs were fabricated using a metal-insulator-semiconductor structure due to a lack of p-type GaN. The first p-n junction GaN LED was demonstrated by Amano et al. using the LEEBI treatment to obtain p-type GaN in 1989. They obtained the current-voltage (I-V) curve and electroluminescence of the LEDs, but did not record the output power or the efficiency of the LEDs. Nakamura et al. demonstrated the p-n junction GaN LED using the low-temperature GaN buffer and the LEEBI treatment in 1991 with an output power of 42 μW at 20 mA. The first p-GaN/n-InGaN/n-GaN DH blue LEDs were demonstrated by Nakamura et al. in 1993. The LED showed a strong band-edge emission of InGaN in a blue wavelength regime with an emission wavelength of 440 nm under a forward biased condition. The output power and the EQE were 125 μW and 0.22%, respectively, at a forward current of 20 mA. In 1994, Nakamura et al. demonstrated commercially available blue LEDs with an output power of 1.5 mW, an EQE of 2.7%, and the emission wavelength of 450 nm. On Oct. 7, 2014, the Nobel Prize in Physics was awarded to Isamu Akasaki, Hiroshi Amano and Shuji Nakamura for “the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources” or, less formally, LED lamps.
By combining GaN-based LEDs with wavelength converting materials such as phosphors, solid-state white light sources were realized. This technology utilizing GaN-based LEDs and phosphor materials to produce white light is now illuminating the world around us as a result of the many advantages over incandescent light sources including lower energy consumption, longer lifetime, improved physical robustness, smaller size, and faster switching. LEDs are now used in applications as diverse as aviation lighting, automotive headlamps, advertising, general lighting, traffic signals, and camera flashes. LEDs have allowed new text, video displays, and sensors to be developed, while their high switching rates can be very useful in communications technology. LEDs, however, are not the only solid-state light source and may not be preferable light sources for certain lighting applications. Alternative solid state light sources utilizing stimulated emission, such as laser diodes (LDs) or super-luminescent light emitting diodes (SLEDs), provide many unique features advantageously over LEDs.
In 1960, the laser was demonstrated by Theodore H. Maiman at Hughes Research Laboratories in Malibu. This laser utilized a solid-state flash lamp-pumped synthetic ruby crystal to produce red laser light at 694 nm. Early visible laser technology comprised lamp pumped infrared solid state lasers with the output wavelength converted to the visible using specialty crystals with nonlinear optical properties. For example, a green lamp pumped solid state laser had 3 stages: electricity powers lamp, lamp excites gain crystal which lases at 1064 nm, 1064 nm goes into frequency conversion crystal which converts to visible 532 nm. The resulting green and blue lasers were called “lamped pumped solid state lasers with second harmonic generation” (LPSS with SHG) had wall plug efficiency of ˜1%, and were more efficient than Ar-ion gas lasers, but were still too inefficient, large, expensive, fragile for broad deployment outside of specialty scientific and medical applications. To improve the efficiency of these visible lasers, high power diode (or semiconductor) lasers were utilized. These “diode pumped solid state lasers with SHG” (DPSS with SHG) had 3 stages: electricity powers 808 nm diode laser, 808 nm excites gain crystal, which lases at 1064 nm, 1064 nm goes into frequency conversion crystal which converts to visible 532 nm. As high power laser diodes evolved and new specialty SHG crystals were developed, it became possible to directly convert the output of the infrared diode laser to produce blue and green laser light output. These “directly doubled diode lasers” or SHG diode lasers had 2 stages: electricity powers 1064 nm semiconductor laser, 1064 nm goes into frequency conversion crystal which converts to visible 532 nm green light. These lasers designs are meant to improve the efficiency, cost and size compared to DPSS-SHG lasers, but the specialty diodes and crystals required make this challenging today.
Solid-state laser light sources, due to the narrowness of their spectra which enables efficient spectral filtering, high modulation rates, and short carrier lifetimes, smaller in size, and far greater surface brightness compared to LEDs, can be more preferable as visible light sources as a means of transmitting information with high bandwidth in many applications including lighting fixtures, lighting systems, displays, projectors and the like. Advancements of new GaN-based blue laser technology based on improved processes have substantially reduced manufacture cost and opened opportunities for utilizing the modulated laser signal and the light spot directly to measure and or interact with the surrounding environment, transmit data to other electronic systems, and respond dynamically to inputs from various sensors. Such applications are herein referred to as “smart lighting” applications to be disclosed throughout the specification herein.